A resorbable, low viscosity, injectable cement is proposed for use in repair of bone fractures. The proposed cement has a two-part formulation. Part A includes an unsaturated polyester, poly(propylene glycol-co-fumaric acid), a vinyl monomer, an HA/Ca-carbonate filler and an accelerator. Part B contains an initiator suspended in a non-reacting fluid vehicle and an inhibitor to control mixing and working time. The use of HA supports osteoconductivity, while acting as a buffer for acidic degradation products. The goals of this Phase II proposal involve optimizing the cement formulation in-vivo and establishing the functionality of the cement. Candidate formulations differing in viscosity will be screened in rats (tibial defect model), prior to evaluation in rabbits (distal femoral osteotomies) and sheep (midshaft tibial defect). Specifically, eight tasks are proposed: 1) synthesis and characterization of PPF, 2) cement formulation, 3) characterization of the chemistry of the candidate cements, 4) mechanical characterization of the candidate cements, 5) material loss by cure in aqueous medium, 6) in-vivo screening of bone cements of varying viscosities in rats, 7) in-vivo histological and mechanical evaluation in rabbits, and 8) in-vivo evaluation of osseointegration and functionality in a sheep model. PROPOSED COMMERCIAL APPLICATION: A biodegradable bone cement that would provide immediate structural support and subsequently allow normal bone healing and remodeling would have immediate orthopedic and maxillofacial applications. The injectable format is critical to ensuring that this cement can also be used in minimally invasive procedures allowing the costs of treatment to remain low. Reasorbability would reduce the potential for long-term implant complications associated with foreign materials and eliminate the need for implant removal.